I recently replaced all of the O-rings in the AC system, replace the AC compressor, and had it recharged At a shop. He said that it held vacuum with no leaking. After a couple days the AC doesn't work anymore. I did notice that after running the jeep with the AC on and turning the vehicle off, I could hear a slight hissing noise coming from the dash. Any ideas what it could be?

 

Give some vehicle info please.

 

98 Jeep XJ 5 speed 4.0i

 

If the noise is under the dash, it is probably the connections to the evaporator core or the core itself. Perhaps leaking once they get cold from AC being on, and shrinking a little.

 

That's sounds reasonable. This jeep was totaled for over two years in a field. I did all the frame work and body work. AC compressor was seized. Replaced that and it worked fine for a week. The. Just went warm. The accumulator and lines to the AC compressor get really cold and sweat. Not sore if that's normal.

 

Anything cold in a warm humid environment will sweat like crazy. Its normal.